A major focus in the abrasives industry today is the development of more efficient abrasive grain having longer lifespan for heavy duty snag grinding (also called "snagging") of ingots and castings of metal (e.g. stainless steels).
As known to us, the presently best abrasive grains (i.e., particulate abrasive material) that are commercially available for heavy duty snag grinding consist of a fused mixture of alumina and zirconia, both of high purity quality. The two most common compositions of these commercial abrasives appear to have approximate Al .sub.2 O.sub.3 :ZrO.sub.2 weight ratios of 3:2 and 3:1. The development of the fused alumina-zirconia grain overcame such deficiencies in prior abrasive grains as the relatively high rates of chipping due to brittleness of fused alumina grain and the relatively high rates of attritious wear due to abrasive softness of zirconia grain.
Despite the above-noted improvements, there still has remained a strong desire of users of the abrasive grains for even further improvements that will afford them significant economic advantage.
While it has been proposed to improve sintered aluminazirconia abrasive grains by including small additions of other oxides (e.g. manganese dioxide) as sintering aids therein, nevertheless the resultant modified sintered grains have been found to exhibit abrasive wear characteristics grossly inferior to those of fused alumina-zirconia abrasive grains. Moreover, sintering aids are inapplicable to the latter grains in view of their fused nature.